Cable size to electric shower

[FsSolutions]

I have a customer whose electric shower has stopped working. It has previously been working fine for a couple of years. No problems before hand, no faults on the board or tripping out.
upon inspection it looks like the supply cable is undersized. He’s asked me if this would have caused the shower fault? as I understand an undersized cable would more likely effect the circuit or MCB an not the appliance itself.

 

[James]

What makes you think the cable is undersized?

 

[Ian1981]

Volt drop can effect the shower if the cable is undersized, resulting in the shower not working correctly but you have stated that it worked fine for a couple of years.

 

[Lucien Nunes]

Undersize cable is most unlikely to be a factor unless it is so drastically undersize that it has melted, or it has burnt out at the terminations. The only likely impact on the shower itself would be a slight reduction in maximum water temperature if the cable is also long and the voltage drop significant.

 

[FsSolutions]

What makes you think the cable is undersized?

Customer believers the cable meeting the shower is 6mm. Should be 8mm. Previously supplied a 9.5kw and was replaced for a 9.5kw. Unsure whether the entire run is 6mm or just the final section.

 

[R-fur]

Want to check your numbers.

 

[FsSolutions]

Customer is trying to c

What makes you think the cable is undersized?

The customer is trying to establish whether the plumber who installed it is at fault for the shower breaking. Plumber says it was like for like. No faults reported during usage. Shower broke after 2 years and now there’s an issue with the cable size. I wasn’t sure whether a smaller cable size would break the shower. My thoughts were it would only effect the cable or trip the fuse

 

[Lucien Nunes]

I've no idea why you would expect undersize cable to trip the MCB! Showers of this power will operate on 2.5mm² T+E and we've seen it done, but the cable gets very hot and floppy. Subject to voltage drop, 2H4 4mm² MICC on the surface is fully rated for the purpose and would be a perfectly good choice. 2H2.5 is just barely undersize but would function perfectly well.

 

[westward10]

If it has an isolator I would be looking there. Has anyone carried out any tests to verify the supply.

 

[FsSolutions]

Agr

I've no idea why you would expect undersize cable to trip the MCB! Showers of this power will operate on 2.5mm² T+E and we've seen it done, but the cable gets very hot and floppy. Subject to voltage drop, 2H4 4mm² MICC on the surface is fully rated for the purpose and would be a perfectly good choice. 2H2.5 is just barely undersize but would function perfectly well.

Agreed. But would it effectively break the shower? I can’t see how?

 

[Lucien Nunes]

No. Excess voltage drop would affect the shower by reducing the maximum heat output, but not damage it. If the shower has electronic controls, then at some critical level of drop, they would stop working and the shower would switch off, or cycle on and off. I would expect it to work at 190V (230V -10% - a bit of leeway) which would typically mean 40V of drop. So when the mains volts are normal, even 150 metres of 6mm² would not stop it working.

 

[Andy78]

If I were you I'd get an electrician in to have a look at the situation to best inform the customer. You seem to be stabbing in the dark without the knowledge necessary to diagnose a problem, perceived or not, especially before connecting a new shower up.

 

[westward10]

Has anyone carried out any tests.

 

[Strima]

Has anyone carried out any tests.

I doubt that very much.

 

[DPG]

When you say you have a customer, what capacity are you acting in?